The use of cells microencapsulated in a polymeric permselective membrane has revolutionized the design of artificial organs and opened up exciting avenues in improving and restoring function in people with physical disabilities. Of particular relevance to the field of rehabilitation engineering are; 1) polymer encapsulated neurotransmitter secreting cells for neurological disorders such as Parkinson's and Alzheimer's diseases, 2) chromaffin cell transplants for alleviation of chronic pain, and 30 encapsulated chondrocytes for reparation of musculoskeletal defects. Delivery of growth factors may also be effected by this approach. Enclosing genetically engineered cells in semipermeable microcapsules allows the use of non-autologous cells for somatic gene therapy. the objective of this proposal is to design new microcapsules that have the desirable substrate characteristics of promoting attachment and maintaining long-term differentiated functions of the encapsulated cells, and have the required transport characteristics of allowing exit of genetically modified gene products but preventing contact between the host's immune mediators and the implanted cells. The microcapsules will be synthesized by a complex coacervation technique. The microcapsules will be composed of a combination of the following components; collagen or poly(dimethyaminoethyl methacrylate) as the polycation, hyaluronic acid or poly(methacrylic acid) as the polyanion, and poly(2-hydroxyethyl methacrylate) as an adjuster of the hydrophilicity of the microcapsules. In all cases, the inside layer of the microcapsules will be composed of either collagen or hyaluronic acid; popular substrates for attachment and maintenance of cell functions of many cell types. The external layer will be composed of synthetic polyelectrolytes, which imparts stability and permits fine-tuning of the transport properties. To optimize the complex coacervation process, we will chemically modify collagen and hyaluronic acid to adjust their pKb and hydrophobicity. The quality of the microcapsules will be studied against the compositions of the membrane component and the process parameters. Fibroblasts will be used as a model cell line for encapsulation tests.